Palin attacked Sen. Obama on Saturday for his brief political relationship with Bill Ayers, a founding member of the radical Weather Underground, which was involved in several bombings in the early 1970s, including attacks on the Pentagon and the Capitol. Obama was a child at the time of the bombings.

Obama and Ayers, now a university professor, have met several times since 1995, when both worked with a non-profit group trying to raise funds for a school improvement project and a charitable foundation. CNN's review of project records found nothing to suggest anything inappropriate in the volunteer projects in which the two men were involved.

Obama campaign spokesman Ben LaBolt said the two had not spoken by phone or exchanged e-mail messages since Obama came to the U.S. Senate in 2005. He said they last met more than a year ago when they encountered each other on the street in a Chicago neighborhood where both live. Fact checking Palin's claim

Palin's attack delivered on the McCain campaign's announcement that it would step up attacks on the Democratic presidential candidate with just a month left before the November general election.

"We see America as the greatest force for good in this world," Palin said at a fund-raising event in Colorado, adding, "Our opponent though, is someone who sees America, it seems, as being so imperfect that he's palling around with terrorists who would target their own country." Watch more on what Palin said »

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She referred to an article in Saturday's New York Times about Obama's relationship with Ayers, now 63. But that article concluded that "the two men do not appear to have been close. Nor has Mr. Obama ever expressed sympathy for the radical views and actions of Mr. Ayers, whom he has called 'somebody who engaged in detestable acts 40 years ago, when I was 8.'" Watch CNN's Truth Squad examine Palin claims »

Riot and bomb conspiracy charges against Ayers were dropped in 1974, and he is now a professor of education at the University of Illinois in Chicago.

Obama campaign spokesman Hari Sevugan called Palin's comments "offensive" and "not surprising" given the McCain campaign's statement that "they would be launching Swift boat-like attacks in hopes of deflecting attention from the nation's economic ills."

With Obama rising in polls while the country struggles in the grip of a financial crisis, Sen. John McCain's presidential campaign decided to shift attention away from the troubled economy and on to issues of his opponent's character, judgment and personal associations, the Washington Post reported.iReport.com: What do you think? Sound off with a video response

"We're going to get a little tougher," a senior Republican operative said, requesting anonymity because he wasn't authorized to discuss strategy. "We've got to question this guy's associations. Very soon. There's no question that we have to change the subject here."

McCain campaign spokesman Brian Rogers told CNN, "We are coming up on 30 days until the election, and there are a lot of unanswered questions about Sen. Obama's judgment."

The Obama camp said the tactic wouldn't work.

"What's clear is that John McCain and Sarah Palin would rather spend their time tearing down Barack Obama than laying out a plan to build up our economy," Sevugan said.